Intraocular pressure ran slightly lower on warmer days in treated glaucoma

Design

Single-centre retrospective longitudinal cohort with mixed-effects model

Population

154 eyes of 77 patients with stable, medically treated POAG in Kyoto

Primary outcome

Association of ambient temperature with IOP

Effect

Estimate −0.029 for temperature (p = 0.003); mean blood pressure +0.021 (p < 0.001)

A Kyoto university hospital analysed 2,655 Goldmann pressure readings from 154 eyes of 77 patients with stable, medically treated primary open-angle glaucoma, followed for a mean of 5.2 years with no change in medication (British Journal of Ophthalmology, 29 September 2026). A mixed-effects model adjusted for ocular, systemic and weather variables.

Pressure was negatively associated with ambient temperature (model estimate −0.029, p = 0.003) and positively with mean blood pressure (0.021, p < 0.001). Time of day, glaucoma type and number of drops also mattered, and season showed a trend.

The effect per degree is small. Its practical value is in interpretation: a pressure that is a little higher at a winter visit, in a patient whose drops have not changed, may reflect the weather rather than failing treatment.

• Consider season and temperature when a stable patient's pressure drifts slightly between visits.
• Record the time of each pressure reading; time of day also affected pressure.
• Confirm a borderline rise on repeat measurement before escalating treatment.
• Base escalation on progression of the disc or field, not a single slightly higher reading.

Why it matters

It gives one more reason not to change drops on a single higher reading.

Don't overread it

The study is retrospective, from one centre, and the effect per degree is small.

The statistics, in plain English

The estimate is a model coefficient: on average pressure was slightly lower for each unit rise in temperature, after accounting for other factors. Statistically clear does not mean clinically large.

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